1. Field of the Invention
The present invention relates to a medium position determination apparatus configured to determine a position where a medium to be used in a game is placed.
2. Description of the Related Art
Patent documents 1 (Japanese Published Unexamined Application No. 2004-195156), 2 (Japanese Published Unexamined Application No. 2004-105321) and 3 (Japanese Published Unexamined Application No. 2004-102953) disclose a technique in which, when an X-array antenna and a Y-array antenna emit radio waves, a magnetic field is generated in an upward direction vertical to a table at a cross point where the X-array antenna crosses the Y-array antenna, so as to read information stored in a wireless IC tag embedded in a gaming chip placed on the cross point. The technique carries out the reading operation by each batting region on the table in series.
In a game such as roulette or blackjack to be played in a casino, a player places one or more gaming chips on one or more betting regions of a betting board of the table to bet the one or more gaming chips and plays the game. Each gaming chip includes a wireless IC tag therein. Information stored in the gaming chip is read by generating a magnetic field from an antenna mounted in the betting board. The reading operation is carried out in series, with respect to all betting regions of the betting board. The reading operation determines where each gaming chip is placed on the betting board.
Magnetic lines of magnetic field generated from an antenna are formed in concentric loops. So, in a case where a plurality of gaming chips is stacked in layers on a betting region, if the magnitude of magnetic field is too small, there is a possibility that information stored in a wireless IC tag embedded in an upper gaming chip is not read because the magnetic lines of magnetic field does not reach the upper gaming chip. On the other hand, if the magnitude of magnetic field is too large, there is a possibility that information stored in a wireless IC tag embedded in a gaming chip placed another betting region adjacent to the betting region on which the stacked gaming chips are placed because the magnetic lines of magnetic field reach the another betting region. Thus, depending on the magnitude of magnetic field, there is a possibility that the reading operation can not surely determine where each gaming chips is placed on the betting board.